Compounded mineral lubricant



COMPOUNDED MINERAL LUBRICANT Raymond P. Nejak, Wilmerding, Pa., and Elmer- Cyphers, Cranford, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application October 1, 1952,

Serial No. 312,642

6 Claims. (Cl. 252-372) The present invention relates to mineral lubricating oil compositions containing an improved combination additive.

As disclosed in patent application Serial No. 279,205, filed on March 28, 1952, in the same of Elmer B. Cyphers, the higher dialkyl phenothiazines are effective detergent additives for internal combustion engine lubricants. They are particularly effective in reducing deposits in the critical ring zone area and piston underhead, but substantial improvements in the ring sticking tendencies of the oil were not obtained with these compounds. Ring sticking contributes materially to over-all deposit formation and loss of engine efiiciency. It is an object of the present invention to provide a means for correcting this disadvantage of dialkyl phenothiazines.

It has now been found, and it is the principal teaching of the present invention, that small amounts of zinc or magnesium naphthenates in combination with the dialkyl phenothiazines give superior performance with regard to ring sticking reduction in engines using oils containing these materials. Moreover, this additive mixture is effective in reducing practically all categories of engine deposit demerit. The amount of metal introduced into the lubricant is comparatively small. Therefore, the quantities of ash formed in use are innocuous, particularly with respect to the possibility of forming on the piston any adherent deposit which might provide a hot spot causing the fuel to pre-ignite with subsequent damage to the piston.

The improvements obtained with the present additives are entirely unexpected. The components apparently cooperate to give synergistic improvements, in ring sticking tendencies and the like, that would not be predicted from the relative mild potency of the individual compounds in these respects.

The dialkyl phenothiazines of the present invention have the following general skeletal formula:

wherein the R groups are alkyl radicals, each having in the range of 4 to 16 carbon atoms, preferably 6 to 12 carbon atoms. TheR groups may be similar or dissimilar but those that are identical in structure are preferred. They are generally located in the 3 and 6 positions with respect to the nitrogen group. The R groups may be straight chain or branched in structure, branched groups being preferred. Specific alkyl groups include butyl, isopentyl, n.-hexyl, tert.-octyl, n-decyl, dodecyl and the like.

The dialkyl phenothiazine may be blended in the mineral lubricating oil in amounts in the range of about 0.05 to 5% by weight, based on the total oil composition, the upper limit being restricted to some extent by the solubility of the particular compound being used. Thus, the dibutyl derivatives may be soluble to the extent of only about 1.0% whereas the higher alkyl derivatives are solu- 2,719,121 Patented Sept. 27, 1955 ble to a greater extent. A preferred concentration is in the range of about 0.1 to 1.5% by weight.

The naphthenates may be the conventional zinc or magnesium salts of naphthenic acids, preferably zinc naphthenate. They may be formed from petroleum naphthenic acids by well-known procedures. Acids having molecular weights in the range of about 200 to 300 are generally suitable. Mixtures of zinc and magnesium naphthenates may be used.

The metal naphthenates are generally blended in the oil in amounts in the range of about 0.1 to 5.0%, based on the total composition. Amounts in the range of about 0.3 to 2.0% are generally preferred in order to maintain the total ash content of the lubricant at a low level and to give a favorable ratio of the two additives.

The additives of the present invention are particularly suitable for aviation engine lubricants, although they will find use as additives for other types of internal combustion engine lubricants, diesel lubricants, etc. Other agents that may be used in the compositions include pour point depressants, viscosity index improvers, oiliness agents, oxidation inhibitors, corrosion inhibitors, and the like.

The invention will be more fully understood by reference to the following example. The example, however, is given for the purpose of illustration only and is not to be construed as limiting the scope of the present invention in any way.

Example I.Aviation C. F. R. engine evaluations Various individual and combination additives were blended in a solvent extracted Mid-Continent aviation oil base stock having a viscosity at 210 F. of about Saybolt seconds, and each blend was evaluated in a C. F. R. engine test. In another evaluation, the base stock per se was tested. The blends contained zinc naphthenate per se, 3,6-dioctyl phenothiazine per se, and combinations of this dialkyl phenothiazine with zinc naphthenate in one case and with magnesium naphthenate in another case. All of the blends containing a metal naphthenate had substantially equivalent ash contents. The metal naphthenates Were derived from petroleum naphthenic acids having an average molecular weight of about 240.

The test consisted of operating the aviation C. F. R. engine for 25 hours at 1800 R. P. M. and 4 brake horsepower. The oils were rated on a demerit system wherein a perfectly clean surface is given a rating of 0 and a rating of 10 is given to the worst condition that could be expected. The results are shown in the following table.

The mixtures of the present invention are efiective in reducing all categories of engine deposit demerit. In particular, ring sticking demerit reduction by the metal naphthenate-dioctylphenothiazine combination is far greater than could be anticipated from the performance of the individual ingredients. The total amount of the combined additive required to obtain the synergistic improvement is substantially less than the total of the additives when used separately.

The lubricating oil base stocks used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from paraflinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as Well as residuals, particularly those from which asphaltic constituents have been carefully removed. The base stocks will usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. The viscosity index may range from 0 to 100 or even higher, although for aviation lubricants, which are the preferred base stocks in the practice of the present invention, the higher viscosity indexes are preferred.

What is claimed is:

1. A lubricant composition consisting essentially of a mineral oil and in the range of about 0.05 to 5.0% by weight of a dialkyl phenothiazine, the alkyl groups each having in the range of 4 to 16 carbon atoms, and in the range of about 0.1 to 5.0% by weight of a compound selected from the class consisting of zinc naphthenates and magnesium naphthenates.

2. A composition as in claim I in which said alkyl groups are identical and have in the range of 6 to 12 carbon atoms.

3. A composition as in claim 2 wherein said alkyl groups each contain 8 carbon atoms.

4. A composition as in claim 1 wherein said alkyl groups are in the 3,6-positions.

5. A lubricating oil composition consisting essentially of a mineral lubricant base, in the range of 0.1 to 1.5% by weight of 3,6-dioctyl phenothiazine, and in the range of 0.3 to 2.0% by weight of zinc naphthenate.

6. A lubricating oil composition consisting essentially of a mineral lubricant base, in the range of 0.1 to 1.5 by weight of 3,6-dioctyl phenothiazine, and in the range of 0.3 to 2.0% by weight of magnesium naphthenate.

References Cited in the file of this patent UNITED STATES PATENTS 2,001,108 Parker May 14, 1935 2,190,648 Cantrell Feb. 20, 1940 2,202,826 Brandes June 4, 1940 2,332,825 Zimmer Oct. 26, 1943 2,587,660 Smith Mar. 4, 1952 2,609,343 Saunders Sept. 2, 1952 

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL OIL AND IN THE RANGE OF ABOUT 0.05 TO 5.0% BY WEIGHT OF A DIALKYL PHENOTHIAZINE, THE ALKYL GROUPS EACH HAVING IN THE RANGE OF 4 TO 16 CARBON ATOMS, AND IN THE RANGE OF ABOUT 0.1 TO 5.0% BY WEIGHT OF A COMPOUND SELECTED FROM THE CLASS CONSISTING OF ZINC NAPHTHENATES AND MAGNESIUM NAPHTHENATES. 